In forming of color paper materials and color negative films, there is a need to provide in the film and paper structures a hardener that will improve the physical properties of the gelatin forming the layers of the photographic materials. The speed of the hardener is important as the more rapidly the hardener works, the quicker the photographic material may be available for use.
In color paper materials the colors are formed by reaction of colorless couplers with oxidized developer. The couplers are combined with permanent solvents and stabilizers prior to color paper formation. The solvents improve the reactivity of the couplers, as well as aiding the dispersion of the couplers in the gelatin. Typical color paper structures are shown in Research Disclosure No. 37038, February 1995.
The improvement in print stability of color papers is of continuing interest. Color papers deteriorate by losing whiteness in the white areas such that the white begins to yellow. Another way that the papers illustrate a lack of stability is if the colors fade. The fading of papers and the yellowing of white areas have been at least partially overcome by the provision for more stable dyes and the use of less reactive solvents and less reactive other photographic elements. Further, materials such as antioxidants have been added to photographic print materials to improve their stability.